Effect of Combined Hole Storage and Blocking Interfaces on the Photoelectrochemical Water Splitting Performance of BiVO₄ Photoanodes

Solar-driven water splitting using a photoelectrochemical (PEC) mechanism is of great practical interest for developing renewable energy systems. In general, BiVO₄ photoanodes are considered to be a promising candidate for efficient PEC solar energy conversion. However, their solar energy conversion performance is negatively affected by the high recombination rate of electron–hole pairs. Despite the development of numerous techniques, combined attempts to engineer both hole-blocking (bottom) and hole-storage (top) interfaces in BiVO₄ photoanodes are still lacking. Here, we demonstrate the role of SnO₂ hierarchical microspheres and ferrihydrite nanosheets as hole-blocking and hole-storage layers for efficient water oxidation by BiVO₄ photoanodes. Furthermore, the key contributions of the size of the SnO₂ hierarchical microspheres and the thicknesses of the BiVO₄ and FN layers, as well as the role of the active area for illumination, are studied through several analytical techniques. The optimized SnO₂@BiVO₄/FN photoanodes exhibited a remarkable photocurrent density of 3.28 ± 0.2 mA/cm² at 1.23 V versus RHE, along with excellent stability (10 h). Overall, the results demonstrate that the proposed fabrication method represents a substantial advancement in the development of affordable water splitting cells.